Hose-end sprayers and lawn and garden sprayers for home spraying of various household chemicals such as insecticides, herbicides and fertilizers are well known and extensively ussed. Basically, such units are relatively simple and inexpensive, using the domestic water pressure from a garden hose to power the spray. Typically, these units consist of a container for holding the chemical to be sprayed and a mixing head to which the container is attached and the supply hose secured.
In general, the mixing head is connected to the chemicals in the container by means of a siphon tube which extends from a mixing chamber into the bottom of the container. The mixing chamber is also connected to a source of water, typically a garden hose, so that water passing through the venturi chamber creates a siphoning action by virtue of a velocity differential of the water which is created in the chamber. The basis of operation of virtually all such unit sprayers is Bernoulli's principle.
Most hose-end sprayers have only one dilution ratio. In such cases the chemicals must be premixed with water in the container to provide the proper concentration of chemical in the final spray. Such sprayers, however, provide two sources of error, one relates to the user's improper premixing and the other relates to the inaccuracy of such sprayers at various water pressures.
A number of commercially available sprayers do provide for multiple dilution ratios. Multiple ratio sprayers typically do not require chemical premixing and directly provide the desired concentration of chemical in the spray. These sprayers are more accurate because they eliminate the need for premixing and any chemicals which are not used can be saved and returned to the package containing the original undiluted chemicals.
Multiple ratio sprayers provide ratio variation by either selectively proportioning the size of the opening in the passageway that extends from the container to the mixing chamber or by varying the size of the air vent opening which controls the siphoning of the fluid from the container. In both cases, a multiple orificed selector, such as a rotatable wheel or slideable stem interposed in the passageway or vent, is used to select the dilution ratio. In practice, it has been found that multiple ratio sprayers that control the air vent orifice size to vary the dilution ratio are not as accurate as those which vary the size of the fluid opening between the container and the mixing chamber. However, the sprayers which vary the size of fluid opening and to some extent those controlling the air vent, are susceptible to plugging caused by chemicals drying in the control orifice rendering them inaccurate or inoperable. Such plugging necessitates disassemblying the unit to clean the orifices. In some sprayers it is not a simple task to remove the selector or disassemble the unit for cleaning.
Illustrative of prior art multiple ratio sprayers are U.S. Pat. Nos. 3,112,884 and 3,191,869.
Accordingly, it is an object of the present invention to provide a multiple ratio hose-end sprayer having a multiple fluid orifice selector dial which is easy to remove for cleaning, but precisely alignable in operation to provide accurate dilution ratios. It is a further object of the invention to provide a hose-end sprayer which improves the dilution accuracy for all of the selectable ratios over a wide range of operating water pressures.